The Triode as a Detector

Author: E.E. Kimberly

When a triode is used as an amplifier, it should be operated in the straight portion of its characteristic curve to insure fidelity of its output. If the grid bias is SO great that the grid potential swings are in the curved portion of the characteristic, as shown in Fig. 27-18, then a positive signal potential will cause a greater change in plate current than will a negative signal potential of the same strength. This phenomenon results in partial rectification and is popularly known as demodulation or detection. Detection is necessary in radio receivers to convert the alternating high-frequency incoming signals to audio-frequency signals to which a telephone receiver or similar instrument will respond.

Fig. 27-18. The Triode Used as a Detector